General magnetic tape has a low recording density because of its low track density. Serpentine type magnetic tape particularly has a low recording density. On the other hand, helical scan type magnetic tape, which uses a servo tracking system called automatic track finding (ATF), possesses a higher track density than the serpentine type magnetic tape.
Servo tracking systems proposed for serpentine type magnetic tape include an embedded servo system, in which servo signals are written on the same track as the data track on the magnetic recording surface, and a system in which a track exclusive to servo signals is provided on the magnetic recording surface. Japanese Patent Publication No. 82626/95 discloses a servo control system particularly useful where the pitch of data tracks is as small as several tens of microns, in which a dedicated track for servo information is provided on the magnetic recording surface and a plurality of servo reproduction heads are used for reading the servo signals. According to this technique, however, the number of serve reproduction heads must be increased as the number of tracks increases. Otherwise, the number of servo tracks should be increased. Like this, conventional servo tracking systems use the same side of magnetic tape as used by data recording, which means that the data recording area is reduced accordingly. This disadvantage is conspicuous in the servo tracking system of Japanese Patent Publn. No. 82626/95 when a track density is as high as about 30 tracks per mm or even more.